Hatena2008-10-25
code:hatena
<body>
*1224895628*Midterm I wrote a program in Haskell to read out the final round. Let's match the results with the ones written in C++.
-----
||
$ time runghc saichugen.hs
real 6m3.271s
user 5m52.644s
sys 0m3.304s
||<
It is strange that a process that takes 4 seconds in C++ and 120 seconds in Python takes 720 seconds in Haskell, even though Haskell is supposed to compile natively.
-----
I was told that sum might cause a huge list of arguments to be expanded in memory, so I wrote this to replace it, but it still takes 6 minutes.
|haskell|
mysum :: Int -> Int -> Int mysum result [] = result
mysum result (x:xs) = mysum (result + x) xs
mysum0 = mysum 0
||<
-----
I translated it almost verbatim into Python to give to id:voluntas.
||
$ time python experiment3.py
real 4m5.894s
user 4m0.529s
sys 0m1.474s
||<
It took me 6 minutes with Haskell, but 4 minutes with Python.
-----
Oh, a comment while I was working on the Python version. Thanks, I see what you mean about using seq and turning off delayed evaluation. I'll give it a try.
-----
|diff|
mysum :: Int -> Int -> Int mysum result [] = result
-mysum result (x:xs) = mysum (result + x) xs
+mysum result (x:xs) = (result + x) seq (mysum (result + x) xs)
mysum0 = mysum 0
||<
||
real 6m38.293s
user 6m27.055s
sys 0m3.467s
||<
Oh my God, I'm late.
|diff|
add :: Score -> Score -> Score
-add (Score x y z) (Score a b c) = (Score (x + a) (y + b) (z + c))
+add (Score x y z) (Score a b c) = (Score (x + a) (y + b) (z + c)) seq (Score (x + a) (y + b) (z + c))
--main = print $ (Score 1 2 3) add (Score 0 3 0)
||<
||
real 6m51.495s
user 6m34.909s
sys 0m4.039s
||<
What the heck...am I using seq incorrectly?
-----
>
runghc runs without compiling.
<<
Oh, it is an interpreter? I thought it was compiled and executed internally.
||
real 0m14.942s
user 0m13.614s
sys 0m0.229s
||<
Wow, it's much faster, about 3-4 times faster than C++, maybe a little faster than C++ if it's paralleled and running on a quad core.
-----
>
I assume from the execution time that you did not have -O2 on at compile time?
<<
||
real 0m1.843s
user 0m1.803s
sys 0m0.023s
||<
Oh wow, it's about 2x faster than the version I wrote in C++! I guess the C++ version is slower because it has it as a VECTOR instead of a list. Even so, I wonder if it changes 2 times.
*1224917666*Pythonsum is eager or not I'm porting because id:voluntas said "I'm porting to Erlang, so I'm writing Haskell code in plain Python" I was wondering if sum is eager, so I'm experimenting.
|python|
class Foo(object):
def __init__(self, i):
print "initialized %d" % i
self.i = i
def __add__(self, v):
print "added %d and %d" % (self.i, v.i)
return Foo(self.i + v.i)
def __del__(self):
print "deleted %d" % self.i
def gen():
for i in range(3):
yield Foo(i)
sum(gen(), Foo(100))
||<
Execution Result
||
initialized 100
initialized 0
added 100 and 0
initialized 100
deleted 0
initialized 1
added 100 and 1
initialized 101
deleted 100
deleted 1
initialized 2
added 101 and 2
initialized 103
deleted 101
deleted 2
deleted 100
deleted 103
||<
You're running 1 or 100 destructors right after you make 101 or something, and since you're not an eager, you can safely shove a huge generator comprehension in there.
*1224918982* Easter egg for python 3.0
import antigravity
The Japanese translation is
Why do you fly, Chiyo-chan?" "Because it's Python.
*1224957031*PySpa
Wow, something like KeyNote is running in the browser with JS. You can export it to PowerPoint or PDF format. Amazing, JS can do all this.
Oh, when I try to post a picture, I can search for it from the internet and post it.
Download PowerPoint or PDF!
-----
DropBox 20GB or whatever it is, free storage.
-----
Can Django documentation be searched in JavaScript? Conveniently convenient.
</body>
<comments>
<comment>
<username>const ()</username>
<timestamp>1224917586</timestamp>
</comment>
<comment>
<username>s</username>
<body>runghc runs without compiling. </body>
<timestamp>1224931958</timestamp>
</comment>
<comment>
<username>tanakh</username>
<body>I'm guessing from the run time that you didn't add -O2 at compile time? </body>
<timestamp>1224939456</timestamp>
</comment>
<comment>
<username>const ()</username>
<body>If we rewrite<br>mysum result (x:xs) = result' seq (mysum result' xs)<br> where result' = result + x<br>add (Score x y z) (Score a b c) = x' seq y' seq z' seq Score x' y' z'<br> where (x,y,z) = (x+a,y+b,z+c)<br>I think. <br>Maybe the optimization will get us there. </body>
<timestamp>1225092242</timestamp>
</comment>
</comments>
---
This page is auto-translated from /nishio/Hatena2008-10-25. If you looks something interesting but the auto-translated English is not good enough to understand it, feel free to let me know at @nishio_en. I'm very happy to spread my thought to non-Japanese readers. ![http://gyazo.com/d6b43a91bbb19b8cb18de5b41eff4359.png">](http://gyazo.com/d6b43a91bbb19b8cb18de5b41eff4359.png">){kind=link}
![http://gyazo.com/4664be707320f4dc77a30cd06f8c8fda.png">](http://gyazo.com/4664be707320f4dc77a30cd06f8c8fda.png">){kind=link}